I can't help with the photo, but I am a student of the Black family! The date is far too late for any of John Ebenezer's uncles, but perhaps a cousin? I have been unable trace his cousin Thomas Black after 1863, who was about the same age. Do you have any info on what made JE throw up his prospects in the family agribusiness to take his chance in the fledgling country?
I assume you have some knowledge of the family history in the UK, but if I can cast any light let me know.